This invention relates broadly to the art of security devices, and more particularly to devices for preventing one door to a transfer chamber from opening when another is already open.
Armed robberies of cashiers in stores, especially those of the fast-food take-out shops, constitute a serious problem. Such holdups can cause a lowering of employee morale to the point that it is difficult to find employees willing to work in questionable neighborhoods or at night in any neighborhood. Further, customers are wary of coming into stores that have experienced holdups.
U.S. Pat. No. 3,669,038 to Watson suggests the use of a transfer or delivery chamber having an attendant and a customer door. The customer door remains closed until the attendant has placed an order in the chamber through the attendant door and closed the attendant door. The customer door is then automatically opened to allow the customer to retrieve the order. A problem with the system described in Watson is that it is unduly complicated, in that it requires a motor and electronic linkage to the motor. Further, it is easily subject to malfunctions which are not easily correctable without utilization of a repairman.
Other U.S. patents which describe two-door chamber systems are: U.S. Pat. Nos. 1,393,149 and 1,403,559 to Matchette; 1,570,207 to Craw; 1,603,404 to Proctor; 1,670,372, 1,673,291, and 1,686,831 to Matchette; 3,054,555 to Saxon; 3,110,438 to Leckner; 3,129,967 to Shoenfeld; and 3,174,193 to Smith.
Although these systems employ mechanical linkages between the doors, rather than electrical linkages as does Watson, most of them require more than one lever and all of them are unduly complicated in structure and operation. In addition, most of these systems appear to be somewhat fragile, lacking in durability and strength, subject to malfunctions and can be easily circumvented.
Thus, it is an object of this invention to provide a two-door transfer-chamber system which is uncomplicated, inexpensive to manufacture, durable, reliable and strong.